taskset - Cheap VPS LLC

TASKSET

NAME

taskset – retrieve or set a process’s CPU affinity

SYNOPSIS

taskset

[options] mask

command [arg]…

taskset

[options]

-p

[mask] pid

DESCRIPTION

taskset

is used to set or retrieve the CPU affinity of a running process given its PID
or to launch a new COMMAND with a given CPU affinity. CPU affinity is a
scheduler property that "bonds" a process to a given set of CPUs on the system.
The Linux scheduler will honor the given CPU affinity and the process will not
run on any other CPUs. Note that the Linux scheduler also supports natural
CPU affinity: the scheduler attempts to keep processes on the same CPU as long
as practical for performance reasons. Therefore, forcing a specific CPU
affinity is useful only in certain applications.

The CPU affinity is represented as a bitmask, with the lowest order bit
corresponding to the first logical CPU and the highest order bit corresponding
to the last logical CPU. Not all CPUs may exist on a given system but a mask
may specify more CPUs than are present. A retrieved mask will reflect only the
bits that correspond to CPUs physically on the system. If an invalid mask is
given (i.e., one that corresponds to no valid CPUs on the current system) an
error is returned. The masks are typically given in hexadecimal. For example,

0x00000001

is processor #0

0x00000003

is processors #0 and #1

0xFFFFFFFF

is all processors (#0 through #31)

Whentaskset

returns, it is guaranteed that the given program has been scheduled to a legal
CPU.

OPTIONS

-p, –pid

operate on an existing PID and not launch a new task

-c, –cpu-list

specify a numerical list of processors instead of a bitmask. The list may
contain multiple items, separated by comma, and ranges. For example,0,5,7,9-11.

-h, –help

display usage information and exit

-V, –version

output version information and exit

USAGE

The default behavior is to run a new command with a given affinity mask:

taskset

mask

command [arguments]

You can also retrieve the CPU affinity of an existing task:

taskset -p

pid

Or set it:

taskset -p

mask pid

PERMISSIONS

A user must possessCAP_SYS_NICE

to change the CPU affinity of a process. Any user can retrieve the affinity
mask.